How do I fix a leaky showerhead?

A leaky showerhead is usually caused by a worn rubber O-ring or washer inside the shower arm connection or the showerhead itself. Unscrew the showerhead from the shower arm. Replace the O-ring or washer with an identical part from a hardware store. Apply plumber's tape to the shower arm threads before reattaching the showerhead. Hand-tighten plus a quarter turn with a wrench wrapped in tape to avoid scratching the finish.